Referring to FIG. 1, a conventional cosmetic applicator 10 (such as an eyeliner) includes a casing 11, an adjusting member 12, a cartridge 13, a core 14, a seat 15 and a brush 16. The cartridge 13 is connected to a rear end section of the adjusting member 12, and includes a tube member 131 containing liquid cosmetic, and a plug member 132 plugged into an open end of the tube member 131 and connected to the adjusting member 12. The adjusting member 12 is formed with an axial hole 121 for insertion of the core 14. The core 14 has a rear end extending through the plug member 132 for absorbing the liquid cosmetic in the tube member 131. A plurality of adjusting plates 122 are provided on an outer surface of the adjusting member 12, and spaces among the adjusting plates 122 are in spatial communication with the axial hole 121 such that the liquid cosmetic absorbed by the core 14 can spread to the adjusting plates 122 for storage and regulation. The seat 15 is sleeved onto a front end of the adjusting member 12 with at least one opening 151 formed in an outer side thereof. The outer side of the seat 15 and the adjusting member 12 cooperatively define a passage 152. Air flows into the passage 152 via the opening 151, and then flows through the core 14 and reaches the adjusting plates 122 of the adjusting member 12. The brush 16 is partially disposed in the seat 15 with a front end thereof protruding from the seat 15, and a rear end thereof connected to the core 14. The liquid cosmetic flows out of the brush 16 after being absorbed by the core 14.
Although the aforementioned conventional cosmetic applicator 10 has an automatic liquid cosmetic flowing effect, there is still room for improvement. Since the adjusting member 12 is only covered by the casing 11, and the tube member 131 is connected to the adjusting member 12 via the plug member 132, the liquid cosmetic accumulated among the adjusting plates 122 might leak through a gap between the adjusting member 12 and the casing 11. In addition, if the airtightness of the coupling between the tube member 131 and the plug member 132 is poor, the liquid cosmetic will leak through a gap between the tube member 131 and the plug member 132, and spread through an internal space among the casing 11, the adjusting member 12, and the cartridge 13, which causes waste of the liquid cosmetic.